1. Field of the Invention
The present invention relates to a drive force transmitting mechanism in which rotational drive force by a rotating shaft member is transmitted to a portion to be driven through a worm gear, more particularly, to a drive force transmitting mechanism in which, for example, drive force necessary for rotating a roller for conveying a photosensitive material in an automatic photosensitive material processing apparatus is transmitted from a drive source.
2. Description of the Related Art
In mechanical drive force transmitting devices, the drive force from a drive source (motor) is often transmitted to a portion to be driven via a gear. As a gear, a spur gear, a helical gear, a worm gear and the like suitable for a mechanical device are properly selected.
A mechanical drive force transmitting device is used, for example, in an automatic processing apparatus for a photosensitive material. In the automatic processing apparatus, an exposed photosensitive material is guided and conveyed by a plurality of rollers in a plurality of processing tanks in which processing solutions are stored in sequence to be processed. These rollers are generally driven by the following manner. A drive shaft driven by a drive source (motor) is disposed in the horizontal direction along a plurality of processing tanks above the processing tanks. A first worm gear adjacent to each of the processing tanks is secured on the drive shaft and the rotation of the drive shaft is transmitted to a shaft vertically disposed in each processing tank through a spur gear meshed with the worm gear. A spur gear is attached to one end of each of the rollers for guiding the photosensitive material and mesh together. One of the spur gears meshes with a second worm gear secured on one end of the vertical shaft. The vertical shaft is rotated so that the drive force is transmitted to the rollers through the second worm gear.
According to the above-described structure, the rollers are rotated through the vertical shaft when the drive shaft is rotated so that the photosensitive material is nipped by the rollers and conveyed along substantially U-shaped conveying paths in the processing tanks.
In the event that drawbacks in transportation, so-called jamming or the like of the photosensitive material are caused, each gear may be damaged due to an excessive load applied to the gear. In a conventional manner, to prevent such damage, when thrust force is applied to the first worm gear, a processing rack supporting a plurality of rollers, a group of spur gears and the shaft, disposed in a processing tank is lifted, so that the mesh of the first worm gear with the spur gear is released and breakage of each gear can be prevented.
However, in the case that the processing rack cannot be lifted, for example, when the processing tank is closely covered by a lid for preventing oxidation of developing solution, just above the processing rack, or when gears or other members fixed to the main body of the automatic processing apparatus are present in the direction of the thrust force acting on the worm gear so that the lifting of the processing rack is prevented, the countermeasures for preventing damage such as the above-described gear tooth breakage and the like cannot be used.
Further, in recent years, the size of automatic processing apparatuses is required to be smaller and a design for securing a space for moving a rack when jamming occurs cannot be adopted.